fuel cut?

[GoRacers]

Just picked up a 78 xs 11. Bike has k&n filters, supertrapp exhaust.

When trying to cruise at a constant speed and rpm, the bike experiences what feels like a fuel cut. Engine note definitely changes, and there is no power. Almost like a cylinder goes out sometimes I can get it back by disengaging and engaging the clutch or shifting up or down. It always goes back to normal if I slow down enough to get into 3rd gear.

When accelerating, the bike pulls really hard. Very smooth, revs up freely and easily, engine acts like it should.

I cleaned the carbs and replaced the diagrams. All jets are clear.

No change, so I am starting to think it may have to do with the way the fuel and vacuum lines are now run, with the aftermarket air filters. I'm also going to inspect the petcocks .

How are the lines supposed to be run when using individual filters?

[TopCatGr58]

Hey there GoRacers,

Well, let's see if I get to be the first one to tell you to look at the Tech Tips, repairs, Electrical, and read thru the PickUp Coil wire repair tip..that sure sounds like what's happening, not fuel!

T.C.

[CaptonZap]

I'll second that. CZ

[natemoen]

Pickup coil wires are broken. As the timing plate rotates it causes the old wire to separate and you lose a cylinder for a moment until the wires touch again. Follow the instructions in this link.

http://www.xs11.com/forum/showthread.php?t=543

For the fuel lines all that you need to do is run a line from the fuel outlet on the petcock (inward facing nipple) to the lower T on either carb pair (1&2 or 3&4) and that is it. It makes it a little easier to use filters if you run the right pair of carbs off the left petcock and vise versa.

The top T on the carb pairs needs to be left open to atmosphere, it is a vent for the carb float bowls.

Also, the petcocks front facing nipples should be plugged into the carb intake boot nipples (usually #2&3) and the other 2 nipples should be plugged. The vacuum advance hose (black vac line coming out of the upper rear of the left side engine cover)needs to be plugged into the nipple that is on the #2 carb body NOT on a intake boot.

[GoRacers]

Hey there GoRacers,

Well, let's see if I get to be the first one to tell you to look at the Tech Tips, repairs, Electrical, and read thru the PickUp Coil wire repair tip..that sure sounds like what's happening, not fuel!

T.C.

I remember reading something about that now. Thanks for the heads up!

[GoRacers]

Pickup coil wires are broken. As the timing plate rotates it causes the old wire to separate and you lose a cylinder for a moment until the wires touch again. Follow the instructions in this link.

http://www.xs11.com/forum/showthread.php?t=543

For the fuel lines all that you need to do is run a line from the fuel outlet on the petcock (inward facing nipple) to the lower T on either carb pair (1&2 or 3&4) and that is it. It makes it a little easier to use filters if you run the right pair of carbs off the left petcock and vise versa.

The top T on the carb pairs needs to be left open to atmosphere, it is a vent for the carb float bowls.

Also, the petcocks front facing nipples should be plugged into the carb intake boot nipples (usually #2&3) and the other 2 nipples should be plugged. The vacuum advance hose (black vac line coming out of the upper rear of the left side engine cover)needs to be plugged into the nipple that is on the #2 carb body NOT on a intake boot.

That's how everything is set up, but I've got to check on those wires.

Thanks everybody. And wow, does this forum move fast!

[skids]

It might be something else, but that is easy to check.

[GoRacers]

Riding it to work this morning, I got some backfiring/popping from the exhaust when the engine came back to life after one of its "fits," so it may be a loss of spark.

Does this pick coil wire problem kill all spark, or a specific cylinder? I'm not losing all power, just 1 (maybe 2?) cylinders. The bike will still accelerate during one of these fits, just noticeably sluggish.

Going to investigate this after work.

[TADracer]

Short answer is yes. These bikes use a wasted spark so when #1 is sparking so is #4 but #4 is on the exhaust stroke. Same for #2 & 3 as they spark together. So a broken pick-up wire can kill two cylinders and do exactly what your motor is doing.

[GoRacers]

Found two broken wires. Quick solder job in both and the it was fixed. Still needs a better tune, but all was well.

Then I guess one of my crappy solders broke, because I lost spark again, for good. Bike would barely idle.

Guess I'll be pulling everything out and soldering it on the countertop to make sure it is good.

Nice to know what the problem is, sucks to fix it twice.

[natemoen]

Make sure you put heat shrink tubing that actually glues onto the wire over the splice. If you get caught in the rain.and the wires get wet they will short out if the water gets to the splice.

[GoRacers]

Ran four new wires, with good solders on the vac advance system. Still don't have spark on two cylinders.

[BA80]

which 2 cylinders?

[GoRacers]

which 2 cylinders?

I pulled the plugs and tested them individually. I am getting spark at each plug, but it is weak. The plugs also look like they may be fouled.

Throwing some new ones in tomorrow, I'll report back.

[GoRacers]

One of my new fuel lines was a bit long and kinked up above the carb. Glad it was something easy, if not a bit embarassing.

Bike runs like a BEAST now.